This invention relates to an apparatus for processing an object in response to or by the use of gas plasma. More particularly, this invention relates to an apparatus which is of the type described and operable in an electron cyclotron resonance (ECR) mode.
An apparatus of the type described, will be referred to herein as a gas plasma processing device When operable in the ECR mode, the gas plasma processing device will be called an ECR device.
Various ECR devices are already known. For example, a few ECR devices are described in the Japanese language in an article contributed by ITOO Yooichi et al of the present assignee to a Japanese technical periodical named "Semiconductor World," 1985 January issue, pages 73, 74, and 103 to 106. In the Itoo et al article, citation is made as regards ECR devices of the types disclosed in Japanese Patent Prepublications (Kookai) Nos. 141,729 of 1980 and 177,975 of 1982. An ECR device is revealed in U.S. Patent Application Ser. No. 845,718 filed Mar. 28, 1986, (now U.S. Pat. No. 4,664,749, issued May 12, 1987) by Atushi Sekiguchi and Hideo Mito, two of the present applicants. Another ECR device is disclosed in Japanese Patent Application No. 69,646 of 1986, filed by the instant assignee for a surface processing method and apparatus therefor invented by the above named Atushi Sekiguchi and Hideo Mito.
In the manner which will later be described in connection with this invention, such a gas plasma processing apparatus comprises a reaction vessel which defines a hollow space. The reaction vessel comprises, in turn, first and second parts defining first and second spaces which are contiguous to the hollow space at an interface. A predetermined gas is introduced at least into the first space. The predetermined gas is, for example, nitrogen. When used, nitrogen may fill both the first and the second spaces. Alternatively, nitrogen may be caused to flow mainly through the first space alone. In this event, silane (monosilane) and/or disilane may be caused to flow through the second space.
A permanent magnet or an electromagnet is disposed around the first part in generating a magnetic field transversely of the interface. A magnetron is used in sending an electromagnetic wave into the hollow space. By cooperation of the electromagnetic wave with the magnetic field, gas plasma is produced in the predetermined gas. The second space is for an object which should be processed in response to the gas plasma.
When nitrogen is used in the first space with silane used in the second space, the gas plasma products are electrons, nitrogen ions, and nitrogen activated species including free radicals and excited species. In response to such plasma products, silicon nitride is produced in the second space.
The ECR device is useful in processing an object having a low capability of withstanding a high temperature. In the ECR device, the first space is used as a cavity resonator for the electromagnetic wave. With this, an electron cyclotron resonance (ECR) condition is achieved in the first space.
Even with the ECR device, the object is bombarded by charged particles, such as electrons and ions. This causes damages to the object. In order to reduce the damages, it has been known to situate a mesh electrode at the interface. The mesh electrode is used to prevent the charged particles from bombarding the object. It is, however, unavoidable that the charged particles bombard the mesh electrode to cause damages to the mesh electrode.